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How do jigs and shaking tables concentrate alluvial gold?

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A worker in safety gear walks beside a conveyor belt carrying ore at the Tanami gold mine in the arid, expansive landscape of the Tanami Desert. — gold processing The Tanami gold mine, Northern Territory, Australia.

Jigs and shaking tables concentrate alluvial gold by exploiting the high density of gold relative to the surrounding sand and gravel.12

Jigging
In this process, a water stream is pulsed upward and downward through a bed of material. This oscillating motion causes the bed to stratify by density, with the heaviest particles—the gold—settling into the lowest layer, while lighter waste material is carried away at the top.3

Shaking Tables
These devices use inclined, often grooved or ridged surfaces that vibrate back and forth at right angles to a flowing stream of water. As the slurry flows down the incline, the material is stratified into heavy and light layers. The vibration further separates the particles in the impact direction, allowing the table to retain the dense gold particles while the lighter sand and gravel are washed over the ridges or grooves.31

Both methods are essential for processing alluvial deposits, which typically require little to no crushing before gravity separation.1